I am getting ready to upgrade my 60 to a 135. I am doing a few upgrades and additions, and one of which I was considering is a kw reactor from two little fishies. Has anyone had one of these? What are your thoughts? Any input is appreciated.

There are two reasons to use them IMO. First is to add calcium to the water. KW is an excellent source of inexpensive calcium.
The second is to counteract PH swings at night. KW raises PH safely if added very slowly. In tanks as old as mine, I fight to keep PH up and this works fine.